Dummy shoulder structure for line stress reduction

ABSTRACT

Semiconductor integrated circuit line structures for improving a process window in the vicinity of dense-to-isolated pattern transition areas and a technique to implement the line structures in the layout process are described in this disclosure. The disclosed structure includes a semiconductor substrate, and a material layer above the substrate. The material layer has a closely spaced dense line structure, an isolated line structure next to the dense line structure, and a dummy line shoulder structure formed in the vicinity of the dense line and the isolated line structures. One end of the dummy line shoulder structure connects to the isolated line structure and another end extends away from the isolated line structure in an orientation substantially perpendicular to the isolated line structure.

TECHNICAL FIELD

The present disclosure relates generally to semiconductor integratedcircuitry technology, and more particularly, to line feature patterns inintegrated circuitry and methods of making the same.

BACKGROUND

Technological advances in semiconductor integrated circuit (IC)materials, design, processing, and manufacturing have enabled scaling ICdevices where each generation has smaller and more complex circuits thanthe previous generation.

Processes for fabricating wafers of integrated circuits consist of aseries of steps by which a set of geometric patterns, determined by thetransistors and their interconnections, are transformed onto numeroussuperimposed layers made of semiconductor, insulating, and conductingmaterials on top of a substrate. The interconnection of superimposedlayers is achieved by connecting conductive lines in the layers withconductive contact holes and vias, the contact holes and vias beingprocessed like plugs perpendicular to the layers where the conductivelines reside. However, as transistors are scaled down to form integratedcircuits with higher levels of integration and faster speeds, physicalphenomena from tight pitch P of circuits impinge the desired performanceof the interconnecting circuitry. In the case of a conductive layer,metal lines ideally should remain at designed widths. However, metallinewidth varies from many factors. For example, some lines shrink orswell because of the optical proximity effect in the lithographicprocess, and other lines change from surface topography differences inregions with different pattern densities, for example, as a result ofuneven loads in a chemical mechanical polishing (CMP) process or anetching process. The optical proximity effect during lithography processgenerates a linewidth bias between isolated and dense features. Processlimitations degrade effective critical dimensions on the wafer. In somecases, an isolated line can be printed much wider than dense lines ofthe same designed width. The linewidth bias induces the film stress atthe dense-to-isolated line transition vicinity (also called the lineestuaries), generating defects known as metal pits, for example, the“copper line voids”. In an extreme case, metal lines may “lift off” orsimply break. Although IC manufacturers have implemented variousstrategies including Optical Proximity Correction (OPC) models andsophisticated design rules in circuitry layout to better controlcritical dimensions, it has been a challenging task to avoid metal linestress defects at the metal line estuaries. Although described as ametal line problem, the line estuary stress also resides in processinglines of poly, dielectric, semiconductors, and other materials.

Therefore, an effective and easy-to-implement technique is desired toreduce line stress at the dense-to-isolated line transitional area in ICprocess and manufacturing.

SUMMARY

One embodiment of the present disclosure includes a line structure in asemiconductor integrated circuitry (IC). The line structure is formed ina layer over a substrate and the line structure includes: a plurality ofa first type of lines, the first type of lines are closely spacedpatterns (dense lines); a plurality of a second type of line (isolatedline) formed in the vicinity of the first type of dense lines; and inaddition, there are a plurality of a third type of lines formed in thevicinity of the first type of dense lines and the second type ofisolated line. The third type of lines connect to the second type ofisolated line and extend in an orientation substantially perpendicularto the second type of isolated line.

Another embodiment of the present disclosure includes a semiconductorintegrated circuitry (IC) having a substrate, an insulating layer formedover the substrate including an interconnecting circuitry such ascontact holes or vias, and a conductive line structure on top of theinsulating layer. The conductive line structure includes a plurality ofa first type of conductive lines that are closely spaced patterns (denselines) connected to the interconnecting circuitry in the insulatinglayer. There are a plurality of a second type of conductive line(isolated line) in the vicinity of the dense lines, and the isolatedline is connected to the interconnecting circuitry in the insulatinglayer. There are also a plurality of a third type of conductive line(conductive shoulder) formed in the vicinity of the dense lines andisolated line, and the conductive shoulder is connected to the isolatedline and is formed in an orientation substantially perpendicular to theisolated line. The conductive shoulder is not connected to theinterconnecting circuitry, such as contact holes or vias, in theinsulating layer. The conductive shoulder is used as a protectivestructure for line processing, therefore the shoulder does not need toelectrically connect to the interconnecting circuitry in the insulatinglayer either below or above the conductive line layer. However, theconductive shoulder can be connected to dummy vias in the adjacentinsulating layer. Dummy vias are non-functional structures built forprocess improvement reasons.

Another embodiment of the present invention involves a method fordesigning a line structure in an IC. The method includes identifying anestuary region in the vicinity of an isolated line and a plurality ofdense lines; and adding a dummy line shoulder in the estuary region,wherein the dummy line shoulder connects to and is substantiallyperpendicular to the isolated line. Identifying an estuary region canincludes step 1: identifying the dense lines having a line width lessthan a predefined width; step 2: identifying spaces sandwiched betweenthe dense lines identified in step 1; step 3: grouping the spacesidentified in step 2 into one block; step 4: defining the edgeboundaries of the block in step 3 as the estuary region; step 5: drawinga first box of a predetermined size using the estuary region and theisolated line as borders; step 6: drawing a second box within a portionof the first box, the second box using the isolated line as a border andkeeping a predetermined distance from the dense lines.

Further embodiments and aspects of the invention are discussed withrespect to the following figures, which are incorporated in andconstitute a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 shows a top view of a line structure.

FIG. 2 is a SEM image showing pit defects in a copper line.

FIG. 3 shows a top view of a line structure closely spaced with aprotective dummification structure.

FIG. 4 shows a top view of a line structure protected with dummy lineshoulders according to some aspects of the present disclosure.

FIG. 5A shows a top view of a transitional line feature protected by afirst dummy structure, and FIG. 5B shows a top view of a transitionalline feature including dummy line shoulders according to a second dummystructure.

FIG. 6 shows a top view of a line structure including dummy lineshoulders according to another embodiment of the present disclosure.

FIG. 7A shows a top view of a metal line structure having dummy metalline shoulders according to some embodiments of the present disclosure,and FIG. 7B is a SEM image of an unprotected metal line structure.

FIG. 8A shows a top view of a metal line structure having dummy metalline shoulders according to another embodiment of the presentdisclosure, and FIG. 8B is a SEM image of an unprotected metal linestructure.

FIG. 9A shows a top view of a metal line structure having dummy metalline shoulders according to some embodiments of the present disclosure,and FIG. 9B is a SEM image of an unprotected metal line structure.

FIG. 10A shows a top view of a metal line structure having dummy metalline shoulders according to some embodiments of the present disclosure,and FIG. 10B is a SEM image of an unprotected metal line structure.

FIG. 11 shows a top view of a line structure including protectiveL-shaped dummy line shoulders according to an alternative embodiment ofthe present disclosure.

FIGS. 12A-D show a process flow for implementing dummy line shoulders inthe vicinity of a line structure according to various embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The present disclosure relates to semiconductor integrated circuitryline feature processing and methods for implementing integratedcircuitry line features. It is understood that the following disclosureprovides many different embodiments, or examples, for implementingdifferent features of the invention. Specific examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. In addition, the present disclosure may repeat referencenumerals and/or letters in the various examples. This repetition is forthe purpose of simplicity and clarity and does not in itself dictate arelationship between the various embodiments and/or configurationsdiscussed. Moreover, the formation of a first feature over or on asecond feature in the description that follows may include embodimentsin which the first and second features are formed in direct contact, andmay also include embodiments in which additional features may be formedinterposing the first and second features, such that the first andsecond features may not be in direct contact.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as being “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. The device may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

Hereinafter, embodiments of the present invention will be explained indetail with reference to the accompanying drawings.

The following descriptions may refer to conductive lines, but thedisclosure is not limited to conductive lines. The conductive lines mayinclude metal lines, such as copper, aluminum, tungsten, platinum, ormany forms of alloys. The conductive lines may also includenon-metallurgical conductive lines, such as semiconductor lines.

In a conductive layer of an integrated circuit, a good processtechnology should produce metal lines that satisfy critical dimension(CD) requirements for a wide variety of patterned feature densitiesresiding in vicinity. One example of a simple transitional linestructure 100 is illustrated in FIG. 1, which shows a top view of aparallel line structure 101 transforming to an isolated single line 102.The line cluster 101 is often referred to as dense lines and the singleline 102 is often referred to as an isolated line. An isolated lineoften is an extension of one of the dense lines in the vicinity of thedense lines. The dense-to-isolated line transitional areas 103 a abovethe line cluster and 103 b at the bottom of the line cluster are oftenreferred to as line estuaries.

Line estuaries present process challenges. Many process limitations fromlithography, etching, polishing, materials, film deposition, and surfacetopography pose severe difficulties to linewidth control at the lineestuaries. For example, an isolated metal line often is printed muchwider than nearby dense lines of the same design width on the samelayer. A sudden linewidth change causes severe film stress at thedense-to-isolated transitional line estuary, resulting in metal linedefects such as film voids. In the extreme case, metal lines may “liftoff” or develop large pits leading to broken lines. FIG. 2 is a SEMimage showing one example of a pit defect in the middle of a densecopper line at the estuary.

Applying Optical Proximity Correction (OPC) models in lithographyexposure improves line printing uniformity in general, but does notreduce linewidth variations sufficiently at the dense-to-isolated linetransitional areas. Sophisticated design rules commonly used incircuitry layout add dummy features around line structures. FIG. 3 showsa top view of a transitional line structure 300 having dummy structures305 a and 305 b fabricated around a dense line cluster 301 and anisolated line 302. However, even at a minimum pitch distance from thedense and isolated lines, dummy structures often prove to beinsufficient in mitigating line stress at the dense-to-isolated lineestuaries. In addition, there are known disadvantages of closely spaceddummy features, for example: 1) the dummy features interfere with thecircuitry's electrical characteristics and distort design RC and/or 2)the tight pitch of the dummy patterning degrades the process window.

Dummy line shoulders in the current disclosure can mitigate line densitytransitional stress without reducing the process window. For example,FIG. 4 shows a top view of a transitional line structure 400 having anexemplary dummy line shoulder structure according to some embodiments ofthe present disclosure. In FIG. 4, four dummy line shoulders, 410 a, 410b, 410 c, and 410 d, are fabricated in transitional areas where a denseline cluster 401 transforms to an isolated line 402. The protectivedummy line shoulders 410 a, 410 b, 410 c, and 410 d connect at one endto the isolated line 402 and extend away from the isolated line 402 inan orientation almost perpendicular to the isolated line 402. Howeverthe shoulders do not have to extend perpendicularly to the isolated line402, as long as the shoulders do not connect to the dense lines 401 orother structures in the vicinity to cause undesirable functional errors.The length of each dummy line shoulder should be long enough to protectthe line estuary area. The dummy line shoulder overall dimensions shouldbe at least at the layer's minimum dimension or pitch so it does notcause additional process challenges. The dummy line shoulders are notelectrically functional features and therefore are not electricallyconnected to interconnecting circuitry in other layers such as contactsor vias. However, the dummy line shoulders can be connected to dummyinterconnecting circuitry in other layers for the purpose of processconvenience. In one embodiment, a dummy line shoulder has a lengthgreater than 1.0 times the sandwiched space between the dense lines 401.

FIG. 5A illustrates a line structure 500 that includes dense lineportions 501 a, 501 b, and 501 c in the middle section, and an isolatedline portion 502 that extends up from the dense line portion 501 c.Dummification features 505 a and 505 b are fabricated around the denseand isolated lines. The dummification features 505 a and 505 b bothinclude many individual dummy features often drawn at or near thecritical dimensional size for the relevant layer.

FIG. 5B illustrates a line structure 550, similar to line structure 500in FIG. 5A, that includes dense line portions 551 a, 551 b, and 551 c inthe middle section, an isolated line portion 552 that extends up fromthe dense line portion 551 c, and an exemplary set of protective dummyline shoulders 553 a, 553 b, and 553 c fabricated at thedense-to-isolated line transitional locations. In the illustratedembodiment, each of the dummy line shoulders 553 a, 553 b, and 553 cconnects to the isolated line portion 552 and extends away from theisolated line portion 552 perpendicularly. In other embodiments, theshoulders do not have to extend out perpendicularly from the isolatedline portion 552, as long as the dummy line shoulders do not connect tothe dense line portions 551 a, 551 b, or other structures in thevicinity to cause undesirable functional errors. Line portion 554extends from portion 551 a via a kink and line portion 554 is not at acritical dimension distance from line 551 c below the line structure,thus in the present embodiment, a dummy line shoulder is not needed forline portion 551 c near line portion 554. In an embodiment where theextended line portion 554 is too close to the nearby line 551 c toprocess the features correctly, a dummy line shoulder may be useful.

The length of each dummy line shoulder should be long enough to protectthe estuary features. The dummy line shoulder overall dimensions shouldbe not smaller than the layer's minimum dimension so it does not causeadditional process challenges. The dummy line shoulders are notelectrically functional features and therefore need not be electricallyconnected to interconnecting circuitry in other layers such as contactsor vias. However, the dummy line shoulders can be connected to dummyinterconnecting circuitry in other layers for the purpose of processconvenience. For simplicity of description, the rules explained in thisparagraph apply to all dummy line shoulders in the following examples.

FIG. 6 shows a top view of an exemplary set of dummy line shoulders nextto a designed line structure according to one or more embodiments of thepresent disclosure. A line structure 600 includes a dense line clustercomposed of parallel lines 601 a and 601 b, two isolated extension lines(an isolated line 602 a above the dense lines and an isolated line 602 bbelow the dense lines), and a separate structure 603 nearby at adistance close to the minimum dimension in the layer. Three dummy lineshoulders 610 a, 610 b, and 610 c are fabricated in line structure 600,where shoulder 610 a connects to the isolated line 602 a at its estuary,shoulder 610 c connects to the isolated line 602 b at its estuary, andshoulder 610 b connects to the middle of line 610 b near the end of 603.Even though line 603 does not extend from line 601 b directly, thelinewidth uniformity of line 601 b is improved by having the protectionof the dummy line shoulder 610 b.

Many varieties of dense-to-isolated line structures, which havelinewidths at or near the process critical dimension limits, can benefitfrom the protection of the dummy line shoulders in the presentdisclosure. FIGS. 7, 8, 9 and 10 illustrate a number of examples wherethe line structures are protected by the dummy line shoulders accordingto one or more embodiments of the present disclosure. Also shown are SEMimages of defected lines with pits and voids near line estuaries,resulting from film stress at the transition.

FIG. 7A shows a top view of a line feature 700 protected by dummy lineshoulders according to some embodiments of the present disclosure. Theline structure to be protected in FIG. 7A includes dense line portions701 a, 701 b, and 701 c in the middle section, an isolated line 702 athat extends up from one of the dense lines 701 c, and another isolatedline 702 b that extends down from one of the dense lines 701 c. Anexemplary set of protective dummy line shoulders 710 a, 710 b, 710 c,and 710 d are fabricated at the dense-to-isolated line transitionallocations, according to some embodiments of the present disclosure. Eachof the dummy line shoulders 710 a, 710 b, 710 c, and 710 d connects tothe isolated lines 702 a, 702 b at one end and extends away from theisolated lines 702 a, 702 b perpendicularly. The dummy shoulders 710 aand 710 b, or 710 c and 710 d, are not aligned at the ends because lines701 a and 701 b are not aligned. However, the dummy shoulders do nothave to extend out perpendicularly from the isolated lines 702 a or 702b, as long as the shoulders do not connect to the dense lines 701 a and701 b, or other structures in the vicinity to cause undesirablefunctional errors. Without the dummy shoulder protection, a line pit wasdeveloped as shown in an SEM image in FIG. 7B.

FIG. 8A shows a top view of a line feature 800 protected by dummy lineshoulders according to other embodiments of the present disclosure. Theline structure to be protected in FIG. 8A includes staggered dense lineportions 801 a, 801 b, 801 c, 801 d, and 801 e in the middle section, anisolated line portion 802 a that extends from dense line portion 801 c,two isolated line portions 802 b and 802 c in between the staggereddense line portions 801 a, 801 b, 801 d, and 801 e, respectively. Anexemplary set of protective dummy line shoulders 810 a, 810 b, 810 c,810 d, 810 e, and 810 f are fabricated at the dense-to-isolated linetransitional locations, according to one embodiment. Each of the dummyline shoulders 810 a, 810 b, 810 c, 810 d, 810 e, and 810 f connects toa line estuary of the isolated line portion 802 a or an isolated section802 b or 802 c, respectively. In the present embodiment, each dummy lineshoulder starts with one end contacting the isolated line or section andextends away from the isolated line or section perpendicularly. In otherembodiments, the dummy shoulders 810 a, 810 b, 810 c, 810 d, 810 e, and810 f do not have to extend out perpendicularly from the isolated line802 a or isolated section 802 b and 802 c, as long as the shoulders donot connect to any of the dense lines 801 a, 801 b, 801 d, 801 e, orother structures in the vicinity to cause undesirable functional errors.Without the dummy shoulder protection, film stress caused a line pit todevelop as shown in a SEM image in FIG. 8B.

FIG. 9A shows a top view of a line feature 900 protected by dummy lineshoulders according to one or more embodiments of the presentdisclosure. The line structure to be protected in FIG. 9A includes adense line cluster composed of lines 901 a, 901 b, and 901 c in themiddle section, and an isolated line portion 902 that extends up fromdense line 901 c. An exemplary set of protective dummy line shoulders910 a and 910 b are fabricated at the dense-to-isolated linetransitional location, according to some embodiments of the presentdisclosure. Each of the dummy line shoulders 910 a and 910 b connects tothe same line estuary of the isolated line 902 from opposing directions,and extends away from the isolated line 902 perpendicularly, forming across-like feature. This cross-like feature is common for an estuarythat has symmetric dense lines ending together on each side of theisolated portion at the transition. However, the dummy shoulders 910 aand 910 b do not have to extend out perpendicularly from the isolatedline 902, as long as the shoulders do not connect to any of the denselines 901 a and 901 b, or other structures in the vicinity to causeundesirable functional errors. Without the dummy shoulder protection,film stress causes a line pit as shown in a SEM image in FIG. 9B.

Some dense line clusters compose closely spaced features that are notlines. One example is illustrated in FIG. 10A, which provides a top viewof a line structure 1000 that includes an irregular dense feature. Theirregular dense cluster includes a short line feature 1001 a, a nearbysmall pad 1001 b, and a line 1001 c sandwiched in between 1001 a and1001 b. An isolated line 1002 extends above the dense line 1001 c andforms an estuary at the transition to the right side. An exemplary dummyline shoulder 1005 is fabricated above the pad 1001 b, according to someembodiments of the present disclosure. Dummy line shoulder 1005 connectsto the isolated line 1002 just above the pad 1001 b and extends awayfrom the isolated line 1002 perpendicularly. However, the dummy shoulder1005 does not have to extend out perpendicularly from the isolated line1002, as long as the shoulder 1005 does not connect to any of the densefeatures 1001 a, 1001 b, or other structures in the vicinity to causeundesirable functional errors. Without the dummy shoulder protection,film stress caused a line pit to develop in one of the unprotected linesnear the close-by pad as shown in a SEM image in FIG. 10B.

A protective dummy line shoulder can also be formed in shapes of an “L”,an “O”, a “U”, or a variety of curves, instead of the straight linesdescribed in the previous paragraphs. One alternative exemplaryembodiment of the present disclosure includes an L-shaped dummy lineshoulder shown in FIG. 11. A top view of a designed feature 1100illustrates a dense line cluster composed of lines 1101 a, 1101 b, and1101 c in the middle section, an isolated line 1102 a that extends upfrom one of the dense lines 1101 c, and an isolated line 1102 b thatextends down from the dense line 1101 c. An exemplary set of protectiveL-shaped dummy line shoulders 1110 a, 1110 b, and 1110 c are fabricatedat the dense-to-isolated line transitional locations. Each of theL-shaped dummy line shoulders 1110 a, 1110 b, and 1110 c connects to oneline estuary at one end of the L-shaped shoulder feature and extendsaway from the isolated line 1102 a or 1102 b perpendicularly. However,the dummy L-shaped shoulders 1110 a, 1110 b, and 1110 c do not have toextend away perpendicularly from the isolated lines 1102 a or 1102 b, aslong as the L-shaped shoulders do not connect to any of the dense lines1101 a or 1101 b, or other structures in the vicinity to causeundesirable functional errors.

FIGS. 12A-D illustrate a step-by-step exemplary flow for implementingthe dummy line shoulder structures in the layout process according toone or more embodiments of the present disclosure. FIG. 12A (Step 1)shows how to define a location where a dummy line shoulder is needed. InStep 1, lines and spaces at or near the critical dimension of therelated layer are identified, and grouped together to form a block withline 1232 sandwiched in between the spaces 1231 and 1233. FIGS. 12B and12C illustrate Step 2 how the estuary boxes are identified. In Step 2,square boxes of a predetermined size are drawn using the edges of theblock and the isolated portions of line 1232 as borders (FIG. 12B). Abox containing a line feature, for example, box 1253, is filtered out(FIG. 12C). A discarded box is not considered appropriate for locating adummy line shoulder because it does not include any isolated structures.As a result only boxes 1251, 1252 and 1254 are the estuary boxes. Thepredetermined size of the estuary boxes is decided by process conditionssuch as critical dimension of the line, dense line pitch, desiredtransitional linewidth correction, and other process parameters in thevicinity of the line features. FIG. 12D illustrates Step 3 when a dummyline shoulder is finally drawn within an estuary box. In Step 3, dummyline shoulder structures 1281, 1282, and 1284 each are created in aestuary box 1251, 1252, or 1254 respectively, the dummy line shouldersconnect and extend away almost perpendicularly from the isolated line,at a defined distance from the estuary side to keep the dummy lineshoulder structure from touching the dense line features. However, thedummy line shoulders do not have to form nearly 90 degree angles fromthe isolated lines. The dummy line shoulders can be straight lines orbending lines such as an L-shaped line.

An experiment on split wafers has been performed to compare printresults of a metal line structure shown in FIG. 1. Each split wasprocessed by applying a different technique. Table 1 summarizes theexperimental results shown as linewidth errors: Split A gets noprotection and has a one-sigma error of −5.7 nm; Split B shows aone-sigma error of −2.9 nm by using the conventional dummificationpatterns spaced 100 nm away from the metal lines; and Split C has aone-sigma error of −1.7 nm, a significant improvement after applying thedummy line shoulder technique, as disclosed in some embodiments of thecurrent invention.

TABLE 1 Summary of linewidth errors in a split wafer experiment SplitCondition Error (nm) A No dummy −5.7 B Dummy w/100 nm space −2.9 C Dummyline shoulder −1.7

The foregoing has outlined features of several embodiments. Thoseskilled in the art should appreciate that they may readily use thepresent disclosure as a basis for designing or modifying other processesand structures for carrying out the same purposes and/or achieving thesame advantages of the embodiments introduced herein. Those skilled inthe art should also realize that such equivalent constructions do notdepart from the spirit and scope of the present disclosure, and thatthey may make various changes, substitutions and alterations hereinwithout departing from the spirit and scope of the present disclosure.

1. A line structure in a semiconductor integrated circuitry (IC),comprising: a substrate; a layer is formed over the substrate, the layerfurther comprising: a plurality of first type of lines including closelyspaced patterns (dense lines); a second type of line (isolated line)formed in the vicinity of the first type of dense lines; and a pluralityof a third type of lines formed in the vicinity of the first type ofdense lines and the second type of isolated line, wherein the third typeof lines connect to the second type of isolated line, formed in anorientation substantially perpendicular to the second type of isolatedline.
 2. The line structure in a semiconductor IC of claim 1, whereinthe lines comprise conductive lines.
 3. The line structure in asemiconductor IC of claim 2, wherein the conductive lines comprise metallines.
 4. The line structure in a semiconductor IC of claim 2, whereinthe conductive lines comprise non-metallurgical lines.
 5. The linestructure in a semiconductor IC of claim 3, wherein the metal linesfurther comprise Cu, tungsten, aluminum, platinum, or alloys.
 6. Theline structure in a semiconductor IC of claim 1, wherein the third typeof lines are formed in an L-shape or an U-shape.
 7. The line structurein a semiconductor IC of claim 1, wherein the third type of linesconnect to the second type of lines like a T.
 8. The line structure in asemiconductor IC of claim 1, wherein the third type of lines connect tothe second type of lines like a cross.
 9. The line structure in asemiconductor IC of claim 1, further comprising functional conductiveplugs (vias) in an insulating layer, wherein the third type ofconductive lines are not directly overlying or underlying vias in theinsulating layer.
 10. The line structure in a semiconductor IC of claim1, wherein the third type of conductive lines are overlying orunderlying a dummy via in an insulating layer.
 11. A semiconductorintegrated circuitry (IC), comprising: a substrate; an insulating layerformed over the substrate including an interconnecting circuitry; aconductive line structure on top of the insulating layer, the linestructure including: a plurality of first type of conductive linesincluding closely spaced patterns (dense lines), wherein the dense linesare connected to the interconnecting circuitry in the insulating layer;a second type of conductive line (isolated line) formed in the vicinityof the dense lines, wherein the isolated line is connected to theinterconnecting circuitry in the insulating layer; and a third type ofconductive line (conductive shoulder) formed in the vicinity of thedense lines and the isolated line, wherein the conductive shoulderconnects to the isolated line, formed in an orientation substantiallyperpendicular to the isolated line, and wherein the conductive shoulderis not directly connected to the interconnecting circuitry in theinsulating layer.
 12. A semiconductor integrated circuitry (IC) of claim11, wherein the conductive lines comprise metal lines.
 13. Asemiconductor integrated circuitry (IC) of claim 12, wherein the metallines comprise copper, aluminum, tungsten, or alloys.
 14. Thesemiconductor integrated circuitry (IC) of claim 11, wherein the densepattern includes a pitch P and the conductive shoulder includes a lengthgreater than about one pitch P.
 15. A semiconductor integrated circuitry(IC) of claim 11, wherein the conductive lines are formed in an L-shapehaving a main segment and a supplementary segment, the main segment issubstantially perpendicular to the isolated line and the supplementarysegment is substantially parallel with the isolated line.
 16. Asemiconductor integrated circuitry (IC) of claim 11, wherein theinterconnecting circuitry in the insulating layer comprises vias.
 17. Amethod for designing a line structure in a semiconductor IC, comprising:identifying an estuary region in the vicinity of an isolated line and aplurality of dense lines; and adding a dummy line shoulder in theestuary region, wherein the dummy line shoulder connects to and issubstantially perpendicular to the isolated line.
 18. The method ofclaim 17, wherein the identifying an estuary region includes: step 1:identifying dense line having a predetermined line width; step 2:identifying spaces sandwiched between the dense lines identified in step1; step 3: grouping the spaces identified in step 2 into one block; step4: defining the edge boundaries of the block in step 3 as the estuaryregion; step 5: drawing a first box of a predetermined size using theestuary region and the isolated line as borders; and step 6: drawing asecond box within a portion of the first box, the second box using theisolated line as a border and keeping a predetermined distance from thedense lines.